Acid fracturing is a widely used technique for increasing the production of oil from a well that penetrates an underground hydrocarbon bearing formation. Typically during an acid fracturing treatment, a pad fluid is injected into the formation so as to create a buildup in wellbore pressure sufficient to overcome compressive stresses and tensile strength of the rock formation. When subjected to a sufficient pressure, the rock fails, allowing a crack, also referred to as a fracture, to form in the formation. Continued fluid injection often increases the fracture's length, height, and width. Acid is then injected into the fracture and the acid chemically reacts with the face of the fracture, etching the face so that when the fracture closes, flow channels are created that extend deep into the formation.
Acid tends to dissolve or etch the first material it encounters, dissolving large pockets of material, which leads to unsupported flow channels that are concentrated near the wellbore, near high permeability areas, or near a region where a delayed-release acid becomes activated or liberated. Unsupported flow channels can collapse upon fracture closure, thereby limiting production.